how to find repeated value and count in mysql - mysql

Question

I have table with 3 columns, now how find value if it appears next 3 times immediately
i.e 1st trnas_value appears in next 3 consecutive times (repeaded 4 times) and 2nd and 6th also rows also repeated the same.date column is sorted from A_Z
date tran_val name
23mar 22 mark
24mar 22 mark
25mar 22 mark
26mar 22 mark
27mar 22 mark
28jan 99 john
29jan 99 john
30jan 99 john
31jan 99 john
output
name trans_value consecutive_count
mark 22 2
john 99 1
we have a code which is not giving the above output..
SELECT name,
tran_val,
MAX(cnt - 3) AS consecutive_count
FROM
(
SELECT date,
tran_val,
name,
#cnt:=IF(#tran_val=tran_val AND #name=name, #cnt + 1, 1) AS cnt,
#tran_val:=tran_val,
#name:=name
FROM some_table
CROSS JOIN (SELECT #cnt:=0, #tran_val:=0, #name:='') sub0
ORDER BY `date`
) sub1
GROUP BY name,
tran_val
any modification in the above code which will get desired output.thanks

Answer 1

Try this:
SELECT `tran_val`, `name`, COUNT(*) - 3
FROM (
SELECT `date`, `tran_val`, `name`, rn - seq AS grp
FROM (
SELECT `date`, `tran_val`, `name`,
#rn := #rn + 1 AS rn,
#seq := IF(#name = `name` And #val = `tran_val`, #seq+1, 1) AS seq,
#name := name,
#val := tran_val
FROM mytable
CROSS JOIN (SELECT #rn := 0, #seq := 0, #name = '', #val = 0) AS vars
ORDER BY `date`) AS t ) AS s
GROUP BY `tran_val`, `name`, grp
HAVING COUNT(*) > 3
You need two separate variable to enumerate sequences:
#rn just enumerates consecutive table rows
#seq enumerates consecutive table rows having the same name, tran_val values.
The difference between these two variables, i.e. #rn - #seq, identifies islands of consecutive table rows having the same name, tran_val values.
Edit: I added a HAVING clause to the query so as to filter out islands having a population of 3 or less consecutive rows.
Demo here